I'm averaging about 14.5 MPG on my new 617.952 install while other G-wagen owners are getting about 20 MPG with the same setup.
I admit, I have a lead foot and I live in a hilly area but even on a day trip for 180 Miles, I still averaged the same.

This is a very low mileage engine in stock configuration. Also has the stock transmission that came with the engine.
The alda still has the factory cover
IP timing is at factory setting using the screw in factory light.
Valve clearances are set to factory specs
Monark injectors set to 2100 PSI pop pressure.
Not much smoke under load but I can see something faint in the rear view mirror.

Aside from MPG, the engine feels just right.

What sort of things should I be looking for?

Fuel leaks and/or odometer accuracy.

what speeds/ RPM's are you running and are your tires pressures low? and is the suspension in alignment?

(02-22-2010 03:23 PM)willbhere4u Wrote:  what speeds/ RPM's are you running and are your tires pressures low? and is the suspension in alignment?

speed - 75-ish with 1:1 top gear
RPM - unknown but maybe high (still no working tach)
suspension and alignment - good
tire pressure - 40psi (5500 lb vehicle)


It might be a little while before I have a tach. I sent mine to Bob Myers so he can fine tune his tach amplifier.

I don't know my diff gearing but I bet I'm running around at 4000 RPM most of the time. Today I was doing a hill climb and normally I gun it but this time I backed off and noticed at a "sweet spot" in the RPM range, the truck would hold it's speed nicely.

Maybe transmission tuning would help a bit.

(02-22-2010 09:48 PM)Syncro_G Wrote:  I don't know my diff gearing but I bet I'm running around at 4000 RPM most of the time. Today I was doing a hill climb and normally I gun it but this time I backed off and noticed at a "sweet spot" in the RPM range, the truck would hold it's speed nicely.

Maybe transmission tuning would help a bit.

I spent the last tank driving with a little less throttle. letting the mid-range pull the G up the hills. result was 16.5 mpg. Wow. still not great but I can see that mileage is tied to RPM's. The old M110 engine couldn't care less where it's throttle was. it was 14 mpg on the freeway, down hill, up hill or putting around the parking lot.

how new are the air and fuel filters, and how about cleaning the injectors. lubro molly makes this stuff called "disel purge", i did to my 84' 300sd and i noticed a little bit of a difference, but that mpg still sounds pretty low, but this is a start.

(03-02-2010 09:15 PM)jagoras Wrote:  how new are the air and fuel filters, and how about cleaning the injectors. lubro molly makes this stuff called "disel purge", i did to my 84' 300sd and i noticed a little bit of a difference, but that mpg still sounds pretty low, but this is a start.

this is a fairly fresh rebuild and install - everything is pretty new.

Is the turbo responding? maby its fueling a ton but isnt getting any help from the turbo.

(03-03-2010 09:04 AM)TotalDiesel Wrote:  Is the turbo responding? maby its fueling a ton but isnt getting any help from the turbo.

That's an interesting thought.
I haven't measured boost pressure but I think I'm getting the expected seat of the pants feel from the turbo.
But you have me thinking...

Ok, I give in. I'm going to pull the automatic and install the 5 speed.
I'm now pulling together parts for the install.
I think I have the flywheel and clutch kit (deal in progress)
have all linkages and slave and stuff from my old 4 speed
Might have a shifter available.
will need to modify my already custom driveshaft (ugh. $$$)

At 75mph with a brick like the G and an IDI engine, I think 14.5 is about right.

Remember, the work done against wind resistance squares with speed, 75mph takes 56% more energy than 60mph. Scaling your results back to 60mph puts you not far from the fuel economy my diesel 4wd gets.